A device that takes inspiration from a spider’s web that may be a game-changer in the control of Type 1 diabetes has been developed by researchers from Cornell University.
Spider's web
The cell encapsulation device developed by the Cornell researchers has enabled the implantation of hundreds of thousands of islet cells into a patient. These cells are derived from stem cells and produce insulin and, as such, can be used as an alternative therapy for diabetic patients. However, long-term immunosuppressive drug administration is usually required with this approach to avoid rejection by the body.
To overcome the immune system’s response to the implantation of islet cells a protective coating is required. The researchers, led by assistant professor Minglin Ma, from the Department of Biological and Environmental Engineering in the College of Agriculture and Life Sciences, used a thin hydrogel coating to protect the islet cells.
The next challenge to this approach came in the form of how the cells could be easily removed once they have outlived their usefulness. This is important as there is the potential of tumour formation with this implantation approach. So, to deal with this issue, the team attached the protected cells to a polymer thread, connecting them altogether and allowing for easy removal.
“When they fail or die, they need to come out,” Ma said in a report on the University’s website. “You don’t want to put something in the body that you can’t take out. With our method, that’s not a problem.”
In the same way that water beads on a spider’s web, the team first of all connected the islet cell-containing capsules through a string. However, it was realised that gaps between capsules were a bad idea for scar tissue and other such complexities. Therefore, the hydrogel layer was placed uniformly around the string instead. The string itself is an ionized calcium-releasing, nanoporous polymer thread.
The completed device starts with two sterile nylon sutures twisted in a helix, which are then folded over to facilitate the subsequent nanoporous structure coatings. The islet cell-containing capsules are then placed onto the structure and don’t slip off due to the twisted and porous design. This thread has been named by the group as TRAFFIC (Thread-Reinforced Alginate Fiber For Islets enCapsulation).
Implantation of the thread would only require minimally-invasive laparoscopic surgery, even though six feet of the thread would be place into the patient’s peritoneal cavity. “We only need two quarter-inch-long incisions,” Dr James Flanders, from the College of Veterinary Medicine, said. “We inflate the abdomen with carbon dioxide, which gives us room to work, and then put in two ports — one for a scope that’s hooked to a camera, so we can see what we’re doing, and the other for a grasping device, which is how we introduce the implant.”
Flanders performed the surgery on canines to assess how retrievable the thread would be and reported that on removal there was either no or minimal adhesion of the device to the surrounding tissues.
Further work is required to determine the specific life span of the thread but currently the team estimates it should last between six and 24 months.
Flanders believes this approach is a potential game-changer in the field, stating: “There have been other devices sort of like this, but this one seems to have so much promise. It’s minimally reactive, it protects the islet cells, it allows them to sense glucose, they don’t attach to anything, and it can be easily removed. To me, it sounded like a win-win.”
The study, ‘Designing a Retrievable and Scalable Cell Encapsulation Device for Potential Treatment of Type 1 Diabetes’, was published on 25 December in Proceedings of the National Academy of Sciences.